The present invention relates to a pressure sensor that converts pressure into an electric signal and outputs it, and a pressure sensor housing for housing the pressure sensor. In particular, the present invention relates to a pressure sensor that is suitably applied to automobiles and the like, and a pressure sensor housing for housing the pressure sensor.
Generally, a semiconductor sensor chip based on the piezo resistance effect is employed in a pressure sensor for use in automobiles. The semiconductor pressure sensor is constructed such that a plurality of semiconductor distortion gages made of materials producing the piezo resistance effect are connected together to form a bridge circuit on a diaphragm formed of single crystal silicon or the like. If the diaphragm is deformed due to a change in pressure, the resistance of the semiconductor distortion gages varies according to the change in pressure. The change in resistance is withdrawn as a voltage signal from the bridge circuit.
FIG. 4 shows the exterior of the above-described conventional pressure sensor, and FIG. 5 is a sectional view taken along line Vxe2x80x94V in FIG. 4. The pressure sensor is constructed such that a semiconductor sensor chip 13 is housed in a concave sensor mount portion 12 formed in a housing body 11, and a pressure port 14 is attached to the housing body 11. The semiconductor pressure sensor chip 13 is electrically connected to a lead terminal (lead frame) 15, which is used for conduction to external devices and is inserted into and integrated with the housing body 11, via a bonding wire 16. The pressure sensor includes a gel protective portion 17 that protects the surface of the semiconductor pressure sensor chip 13 and the bonding wire 16 from contaminated substances included in a medium whose pressure is to be measured. A space between the housing body 11 and the base of the pressure port 14 serves as a pressure detecting chamber 18.
In the pressure sensor constructed in the above-mentioned manner, however, the part of the gel protective member 17, which covers the semiconductor pressure sensor chip 13, is exposed into the pressure port 14. Therefore, degraded and solidified foreign matter such as oil and gasoline included in the medium to be measured may enter the pressure detecting chamber 18 via the pressure port 14 to directly collide with the gel protective member 17. If the foreign matter collides with the gel protective member 17, the impact of the collision is transmitted to the semiconductor pressure sensor chip 13 to cause the deformation amount of the diaphragm to deviate from accuracy. This results in inaccurate measurement of pressure.
Therefore, it would be desirable to provide a pressure sensor that is capable of preventing foreign matter included in a medium to be measured from entering a pressure detecting chamber housing a sensor element that converts pressure into an electric signal so as to eliminate the adversary effect caused by collision of the foreign matter with the sensor element or the like and enable accurate measurement of pressure. It would further be desirable to provide a pressure sensor housing that is capable of preventing foreign matter from entering a pressure detecting chamber housing a sensor element that converts pressure into an electric signal.
In accordance with the present invention, a pressure sensor is provided which includes a sensor element that converts pressure into an electric signal, a pressure detecting chamber that houses the sensor element, a pressure port that allows communication of the pressure detecting chamber and a space in which pressure is to be measured, and a protective portion provided inside the pressure port in such a position as to substantially close an inlet of the pressure detecting chamber in the state in which the pressure detecting chamber and the space in which pressure is to be measured are in communication with each other. According to the present invention, the protective portion provided inside the pressure port substantially closes the inlet of the pressure detecting chamber housing the pressure sensor element in the state in which the pressure detecting chamber and the space in which pressure is to be measured are communication with each other. Therefore, the protective portion prevents foreign matter from entering the pressure detecting chamber